In April, 1986, galvanized sheet metal (26 gauge) was used
to divide each of the 10 soil mixtures into 64 experimental plots, each of
which was 0.75m x 0.75m. To do this, the sheet metal, which was 25cm tall,
was driven into the soil to a depth of 23cm. The entire garden was then
fenced to a height of 2m and to a depth of 1.3m belowground to exclude all
mammalian herbivores.
Fertilization
Fertilizer is mixed and spread by hand once a year, in
early May. Each plot gets the same fertilizer mixture except plot 5. Plot 5
receives NH4NO3, on the first of every month from April to August. Fertilizer added to plot 5 for the last time in April 1994. For further information, see fertilization details.
Mammal Trapping
Small mammals are trapped in the fall to discourage
overwinter inhabitants. Pocket gophers are trapped out of the experiment as
soon as they appear (very infrequent).
Watering
All plots are watered to receive at least 1.5cm/wk in
April, May and October, and 2.5 cm/wk in June through September.
Light
Plots 12-14 were covered with light reducing shade cloth. The
shades were put up in mid-April and were taken down in mid-October. Plot 12 had
the lightest shade, letting the most light through. Plot 13 had the heaviest
shade, letting the least light through. Plot 14 had a shade midway between
the shades on plots 12 and 13. This part of the experiment was terminated in
1992.
Burning
In 1990, plot 11 was burned.
Weeding
All plots and aisles are routinely weeded to keep the area
free of unwanted plants and future seed sources.